Ginkgo – Ginkgo is an Asian plant whose leaves are believed to aid in memory and circulation. Ginkgo bioactives vary considerably with growing conditions, but various studies have shown improvements in health of the circulatory system including lower blood pressure and improvements from deleterious circulation effects of exercising at high altitude.

Ginseng – Ginseng active ingredients come from the roots of the Ginseng plant. It is often present in energy drinks with caffeine and high amounts of sugar. There is not substantial evidence that ginseng alone has any significant ergogenic properties.

Green tea – Epigallocatechin-3-gallate (EGCG) is a flavonoid that is present in high levels in green tea. EGCG supplementation has demonstrated some benefits in performance of endurance events, but more research is necessary to determine the mechanism(s) of action and the amounts of green tea required to achieve a benefit.

Garlic – There is substantial evidence that high amounts of garlic (6-10 g/day) improve peripheral circulation. Even higher quantities (approximately 18 g of garlic or 6 fresh cloves) are associated with lower risks of colorectal and stomach cancers. In addition, there are preliminary data that show that garlic may increase sports performance by delaying fatigue but these data still need to be confirmed in humans.

Glandulars – Glandulars are extracts from animal glands including the thyroid gland, the adrenal gland, the testis, and others. Due to their high amounts of specific hormone, they are thought to increase the activity of that gland in the consumer. Hormones, however, are broken down during digestion, and there has not been any scientific evidence yet that any of these glandulars are effective in sports performance.

Interpretation of findings/Key practice applications:

When consuming or studying herbal supplements, one must remember that bioactive compounds can vary drastically with the growing conditions of the plant. At this point, concentrations of bioactives are not regulated in most herbal supplements and one cannot rely on uniformity from one batch to the next. Hopefully, this will change in the future as scientists further identify the active compounds in foods/supplements and are able to produce more consistent products. It is imperative for the bioactive to reach its target tissues so, in the case of the glandulars specifically, it should be advised to wait to see performance benefits in a controlled scientific study before investing in these agents. With ginkgo, ginseng, green tea, and garlic, these foods are all of plant nature and have been consumed by humans for many generations. It is very likely that the risk of side effects occurring from regular use is low. However, extracts and concentrated forms of these same agents have an increased potential to cause harm. One must be cautious if ingesting large amounts of bioactive compounds. Of the 5 supplements reviewed here, the authors concluded that green tea has the highest potential to demonstrate ergogenic effects from habitual use.